Wszystkie pola: instability

Skocz do pozycji: 1.

Tytuł:: Instability regions of a prestressed compound column subjected to a follower force
Autorzy:: Przybylski, J.
Tematy:: natural vibrations
prestressing
divergence instability
flutter instability
compound column; Pokaż więcej
Wydawca:: Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
Powiązania:: https://bibliotekanauki.pl/articles/279605.pdf Link otwiera się w nowym oknie
Opis:: The influence of prestressing and bending rigidity distribution between rods of a non-linear column on its natural vibrations and stability is studied. The perturbation method is used for solving the problem. Regions of divergence and flutter instabilities for a column have been determined on the basis of courses of eigencurves as a function of bending rigidity ratio and prestress rate. Discontinuities of the critical force have been observed for certain values of the investigated parameters leading to instability of the column, even for small values of the external load. Although each prestress reduces the critical force, it can be applied to passive vibration control.
W pracy zbadano wpływ wstępnego sprężania i asymetrii rozkładu sztywności na zginanie między prętami geometrycznie nieliniowej kolumny dwuprętowej na drgania takiego układu. Do rozwiązania zagadnienia zastosowano metodę małego parametru. Wyznaczono obszary niestateczności dywergencyjnej i fluterowej na podstawie przebiegów krzywych wartości własnych w odniesieniu do relacjimiędzy sztywnościami i stopniem sprężenia. Zaobserwowano skokowe zmiany wartości siły krytycznej dla pewnych wartości obu parametrów prowadzące do niestateczności układu przy niewielkiej sile zewnętrznej. Mimo tego, że każde wstępne sprężenie obniża wartość siły krytycznej, może być wprowadzane w celu pasywnej kontroli częstości drgań.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 2.

Tytuł:: Assessment of slope instability and its impact on land status: a case study from Central Himalaya, India
Autorzy:: Pande, A.
Tematy:: slope instability
erosion hazards
mass wasting hazards
anthropogenic hazards
potential instability/degree of instability
Himalaya; Pokaż więcej
Wydawca:: Stowarzyszenie Geomorfologów Polskich
Powiązania:: https://bibliotekanauki.pl/articles/294330.pdf Link otwiera się w nowym oknie
Opis:: Tectonic instability, geological sensitivity along with human intrusion in Himalaya has greatly exacerbated the occurrence of hazardous situation. Dynamics of slope instability have been evaluated under three processes leading to geomorphic instability, viz. i. erosion ii. mass wasting and iii. anthropogenic. Their causative factors have been identified under Ghuniyoli Gad watershed. The measurement of the intensity, magnitude and nature of instability factors were done within the units of 1 km2 under 21 units of watershed. Each unit was evaluated in terms of type, extent and corresponding degree of instability along with their potential assessment. The stage of erosion reveals that Ghuniyoli Gad watershed experiences instability. Maximum units fall under instability of degree 1 and degree 2 (38% and 38%) while minimum units belong to instability of degree 4 (4.76%). The instability of degree 3 contributes only about 19.04%. Appropriate mitigation measures to overcome hazardous calamities are needed to be introduced therein.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 3.

Tytuł:: Absolute instability of compressible three-dimensional flow
Autorzy:: Tuliszka-Sznitko, E.
Tematy:: numerical simulations
compressible flow
instabilities
absolute instability; Pokaż więcej
Wydawca:: Politechnika Gdańska
Powiązania:: https://bibliotekanauki.pl/articles/1954544.pdf Link otwiera się w nowym oknie
Opis:: In the present paper the instability character (absolute/convective) of compressible viscous flow around geometries rotating in uniform flow is analysed. The linear local stability theory is used to investigate the boundary layer stability. Following the works of Briggs and Bers in the field of plasma physics, the absolute instability region is identified by singularities of dispersion relation called pinch - points. Calculations have been made for different Mach numbers and wall temperatures.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 4.

Tytuł:: Absolute instability in the compressible flow around a rotating cone
Autorzy:: Tuliszka-Sznitko, E.
Tematy:: laminar-turbulent transition
instability; Pokaż więcej
Wydawca:: Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
Powiązania:: https://bibliotekanauki.pl/articles/279579.pdf Link otwiera się w nowym oknie
Opis:: In the present paper the character of instability of compressible viscous flow around geometries rotating in the uniform flow is analyzed. The linear local stability theory is used to investigate the boundary layer stability. Following the works of Briggs and Bers in the field of plasma physics, the absolute instability region is identified by the singularities of dispersion relation called pinch-points. The regions of absolute instability in boundary layers of a rotating cone have been found. Calculations have been made for different Mach numbers, wall temperatures and rotational speeds of the cone.
W pracy badany jest charakter niestabilności przepływu wokół wirującego stożka. Do badania charakteru przepływu zastosowano kryterium fizyków plazmy Briggsa i Bersa, zgodnie z którym o charakterze niestabilności decydują osobliwości funkcji dyspersji zwane punktami styku. Obliczenia przeprowadzono stosując liniową teorię niestabilności. W pracy stwierdzono występowanie obszarów o niestabilności absolutnej w przepływie wokół wirującego stożka. Obliczenia zostały wykonane dla różnych liczb Macha i różnych temperatur ścianki. Wyznaczono krzywe neutralne ograniczające obszar przepływu o niestabilności abolutnej. Stwierdzono, że współczynnik wzmocnienia absolutnego maleje wraz z rosnącą liczbą Macha, jak również malejące pod wpływem chłodzenia ścianki. Nie stwierdzono występowania niestabilności absolutnej w przepływach naddźwiękowych.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 5.

Tytuł:: Inertial elastic instability of rotating nano disks
Autorzy:: Güven, Uğur
Tematy:: nonlocal elasticity
inertial instability
rotating disk
critical speeds; Pokaż więcej
Wydawca:: Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
Powiązania:: https://bibliotekanauki.pl/articles/279481.pdf Link otwiera się w nowym oknie
Opis:: In this work, the static inertial-elastic instability of rotating nano disks is investigated with the centrifugal force formulation considering the radial displacement. Thus, Brunelle’s previous local solution is generalized by using Eringen’s nonlocal elasticity theory. The variations of critical rotation speeds with the nonlocal scale parameter are illustrated under different boundary conditions. It is seen that the critical rotation speeds decrease as the nonlocal scale parameters increase for all cases. Also, it is remarkable that the presented results are affected significantly from the boundary conditions.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 6.

Tytuł:: Instability line as a basic characteristic of non-cohesive soils
Autorzy:: Świdziński, W.
Mierczyński, J.
Tematy:: liquefaction
cyclic mobility
instability; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Budownictwa Wodnego PAN
Powiązania:: https://bibliotekanauki.pl/articles/241208.pdf Link otwiera się w nowym oknie
Opis:: In the paper, the experimental results of undrained response of non-cohesive soil subjected to either monotonic or cyclic loading, are analysed and discussed. The analysis was based on the results of comprehensive testing programme made of "Skarpa" sand investigated in the triaxial compression. Two main undrained behaviours such as liquefaction and cyclic mobility were experimentally identified and studied. In the analysis of undrained behaviour, the concept of steady state of deformation has been adopted. It was shown that the undrained response of non-cohesive soils is governed by different failure mechanisms than in the case of drained samples. In undrained failure mechanism, an important role is played by an instability line, which may be identified with the initiation of potential liquefaction.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 7.

Tytuł:: Towards a proverbial explanation of political instability in independent Nigeria
Autorzy:: Aremu, Johnson Olaosebikan
Tematy:: political instability
proverbs
corruption
nigeria
ethnicity; Pokaż więcej
Wydawca:: Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
Powiązania:: https://bibliotekanauki.pl/articles/1182946.pdf Link otwiera się w nowym oknie
Opis:: The challenge of political instability in Nigeria has defied all solutions till date. The National Youth Service Scheme introduced in 1973 and the Federal Character principle entrenched in the Constitution since 1979, among others, have failed to engender peace and stability in the polity. Judging from this, this paper offers a possible explanation for the seeming failure of all efforts to combat the monster of political instability in Nigeria since independence. Given the fact that most Nigerian leaders and commoners alike are always quick in reverting to some proverbs to rationalize their actions or inactions; five of the most widely acclaimed causes of political instability in Nigeria were examined vis-à-vis some selected Yoruba proverbs. This was done against the backdrop of a Yoruba proverb: Owe lesin oro, oro lesin owe; b’oro ba sonu, owe la fi n waa. (“A proverb is like a horse: when the truth is missing, we use a proverb to find it”). A thorough analysis reveals that political instability in Nigeria has its philosophical foundations well entrenched in the spirit of selected Nigerian proverbs and concludes that political stability may continue to elude the country as long as citizens indulge in hiding under the cover of the letters and spirit of selected Nigerian proverbs to perpetrate evil in governance.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 8.

Tytuł:: Les chamanes contemporains – figures d’instabilité
Contemporary shamans: figures of instability
Autorzy:: Donnarieix, Anne-Sophie
Tematy:: shamanism
instability
hybridization
contemporary French literature; Pokaż więcej
Wydawca:: Katolicki Uniwersytet Lubelski Jana Pawła II. Wydawnictwo Werset
Powiązania:: https://bibliotekanauki.pl/articles/483538.pdf Link otwiera się w nowym oknie
Opis:: Antoine Volodine and Christian Garcin both make a distinctive use of shamanism in fictional novels. By multiplying shaman characters and intertwining the shamanistic principles and the narrative, they develop a poetic of instability noticeable through various hybridization processes notably strengthened by the intrusion of supernatural elements. The analysis of three motives in which this game of unstable balance is particularly mirrored – identity, History and fiction – shall turn our attention to the role of shamanism as a vector of fictional dynamism.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 9.

Tytuł:: Unitary government and the challenge of political instability in Nigeria, 1966-1970
Autorzy:: Aremu, Johnson Olaosebikan
Tematy:: Aguiyi Ironsi
Unitarism
Civil War
Federalism
Political Instability; Pokaż więcej
Wydawca:: Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
Powiązania:: https://bibliotekanauki.pl/articles/1191450.pdf Link otwiera się w nowym oknie
Opis:: Aguiyi Ironsi’s attempted restructuring of Nigeria through the Unification Decree of 1966 might have been well-conceived as a political stabilization and unity oriented policy especially given the turbulence that characterized the country’s First Republic and the circumstances surrounding his emergence as Nigeria’s military leader in January, 1966. However, the introduction of the ill-fated unitarism in replacement of federalism inadvertently further destabilized the country. Northerners became pessimistic about the dictates of the new political arrangement and were vehemently suspicious of the rationale for its introduction. The conflicting interpretations of the Decree eventually led to the fall of Ironsi’s government in July 1966, precipitating the problems of legitimacy, distrust and violence that formed the bedrock of the Nigerian civil war of 1967-1970. This paper therefore explores Nigeria’s political system before Ironsi, rationale for his Unification Decree and the unfolding chain of events that led to Nigeria’s war of unity.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 10.

Tytuł:: Proposition of a new classification for scapholunate instability
Autorzy:: Elsaftawy, Ahmed
Tematy:: scapholunate instability
scapholunate ligament tear
scapholunate dissociation
rotatory subluxationa of scaphoid
new classification; Pokaż więcej
Wydawca:: Index Copernicus International
Powiązania:: https://bibliotekanauki.pl/articles/1396494.pdf Link otwiera się w nowym oknie
Opis:: Scapholunate (SL) instability is the most common pattern of instabilities in the wrist. If untreated or undiagnosed, it may lead to degenerative changes with SLAC (scapholunate advanced collapse) wrist. There are a few of of well-known SL instability classifications. The one that takes into account a dynamic or static nature of SL instability is the most accepted and used. The arthroscopic classifications are also becoming more and more popular. The aim of the study was the critical review of most popular classifications of SL instability, yet at the same time we proposed a new SL instability classification. Results. The new classification was found to be very useful in the process of diagnosis and decision making concerning further treatment of patients with SL instability in our department. Conclusions. The proposed new classification combines the opportunity of evaluating the scapholunate interosseus ligament (SLIL) tear and lesions of the secondary static stabilizers of SL ligament complex that can coexist with or without DISI deformity (Dorsal Intercalated Segmental Instability).
Dostawca treści:: Biblioteka Nauki

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